Ford's seniority -- and his 35 years in the executive ranks -- position him as standard-bearer for Mulally's cultural changes and mentor to Ford executives. He has been chairman since 1999 and is ensconced as head of the family that, through its fabled Class B stock, has effective control of the company.

The company declined to make Ford available for an interview. But associates and former colleagues say the last eight years prepared him to better guide the company through a major transition than during the dark days early in the last decade. After the painful ouster of Jacques Nasser in 2001, Bill Ford struggled with the demands of being CEO. He stepped aside in 2006, handing the job to Mulally.

Nick Scheele, 70, who retired as Ford's COO in 2005, stays in touch with Bill Ford. Scheele says Bill Ford has "immense faith" in Fields but also has the self-confidence to "step in if things start going wrong."

"He's got people he's known for 35 years who are not in management control positions," he says. "He'll be getting feedback from a lot of people. He'll know pretty quickly if it's not working."

Allan Gilmour, 80, former Ford vice chairman who retired in 2005, believes the Bill Ford-Mark Fields pairing will make an "ideal combination." Gilmour, who also communicates with Bill Ford, was Bill Ford's boss in the late 1980s.

"The fact that Bill has been there and has had the [CEO] job is useful," Gilmour says. "He saw all the things that happen and don't happen. I think it's a very good combination of backgrounds and skills.

"Bill brings the historical perspective that is almost unparalleled in American business. He's been on the board since late '88. He's seen the good times and the bad times in a cyclical industry."

But at the same time, it's not easy being executive chairman of one of America's most-revered industrial dynasties, Gilmour says.

"Those are lonely jobs," he says. "Who do you talk to?"

Grooming Fields

Ford will be talking plenty with Fields. Mulally and Ford both worked carefully to groom him for the CEO job. Fields, a 26-year Ford veteran, has spent seven years as the head of Ford's North American operations, leading the unit to record profits before being appointed COO in 2012. He worked internationally with jobs at Mazda and Ford's former Premier Automotive Group of luxury brands.

"He is a very strong executive," says Gerald Meyers, professor at the Ross School of Business at the University of Michigan. "He takes no prisoners. He stands for no nonsense."

But now, Fields must prove himself as a CEO. And he'll be doing that under the watchful eye of Bill Ford.

Franklin McLarty, CEO of RML Automotive, a dealership group in Little Rock, Ark., says Mulally "has done everything right" in preparing Fields for the CEO job. But he adds that Fields needs to draw on Bill Ford's knowledge.

"Mark has proven to be smart," McLarty says. "If he's smart in the way he approaches it, he will engage and rely on Bill Ford as a collaborator as they take Ford forward."

McLarty, whose group has three Ford franchises, says he is "cautiously optimistic."

Another dealer is more guarded: "Bill quickly took the stance: 'In Alan we trust.' Bill's been burned by CEOs in the past. Do they really have complete confidence in [Fields]? I think that leash will be a little shorter."

A coach, not a king

Bill Ford is the third Ford to lead the company bearing the family name. Henry Ford and Henry Ford II preceded him. Unlike those two, who ruled with an iron fist, Bill Ford governs by consensus, consultation and conscience. He was an avowed environmentalist when many auto executives ridiculed green types. And he broke the alpha-exec mold in 2006 by recruiting Mulally to replace him as CEO.

Says Dave Cole, chairman emeritus of the Center for Automotive Research in Ann Arbor, Mich.: "He is a Ford who has an ego totally under control, which is one of his great assets."

Cole says Ford's style is well-suited to the 21st century, in which companies choose executives who fit the coach-mentor mold instead of the regal command-and-control model of last century's auto barons.

"Bill brings the historical perspective that is almost unparalleled in American business. ... He's seen the good times and the bad times in a cyclical industry."

Allan Gilmourformer Ford vice chairman

"Kings are always looking for important people to talk to. They don't waste their time with peasants," Cole says. "Coaches have time for everybody. That is Bill. That is Alan, and I'd be willing to bet that is Mark."

Like his grandfather Edsel Ford, Bill Ford has always been something of a renaissance man. Edsel Ford moved from the Detroit suburb of Dearborn to Grosse Pointe Shores to escape the shadow of his domineering father, Henry Ford I. Bill Ford made a similar break with family tradition.

"He moved from Grosse Pointe, where everyone knew who Bill Ford was, to Ann Arbor, where he's just another person," Cole says.

His interests range far beyond the car business. Ford is vice chairman of the Detroit Lions and led the effort to build Ford Field, the team's environmentally friendly home in downtown Detroit. An avid sportsman, he plays tennis and ice hockey, and he fly-fishes. He is a black belt in tae kwon do.

Some predict that Bill Ford will dive into strategy now that the One Ford plan is up and running worldwide.

'The right thing'

Bill Ford once reflected that "Everything I do as CEO -- and I have learned this kind of the hard way, in the first six months on the job -- every decision upsets somebody. And so all you can do is stay true to your principles and do what you think is the right thing and let the chips fall where they may."

While Ford was a reluctant day-to-day CEO, he is more at home diving into strategic issues. Some predict he will chart strategy now that Mulally's One Ford plan is up and running around the globe.

Says Scheele: "He's one of the best strategists I've ever come across. I think he'll know what the sensitivities are."

Jim Seavitt, owner of the Village Ford dealerships down the street from Ford world headquarters in Dearborn, says: "He'll be up there at that level for a lot of the advanced planning. If Alan was at 50,000 feet, Bill's up at 75,000 feet."

Ford's speeches and remarks offer a clue as to what his 75,000-foot priorities might be.

"In my lifetime, I can actually see where we're going to solve the environmental impact of cars," he told journalists in 2012. "But an 11-day traffic jam with clean cars is still an 11-day traffic jam," he said, referring to an epic 2010 traffic snarl in China's Hebei province.

After the industry solves the environmental issue, Bill Ford went on to say, it will face the congestion problem -- "and we'll solve that, too."

Heavy schedule

But Ford may have to keep a close eye on operations in the near term. Mulally is leaving amid the most ambitious vehicle launch program in Ford's history: 16 new vehicles in North America and 23 worldwide this year. The most daring is the aluminum-bodied 2015 F-150 pickup.

The big plan will provide an early test for Fields, who has a tough challenge anyway in following Mulally.

Says Cole: "The last thing I would want to do is replace a legend. You have the continuity built into the organization because of its success, and you have the ultimate policeman there in Bill. He knows what has worked."

Bill Ford clearly values a smooth transition. At the May 1 announcement that Fields would become CEO, he reflected somewhat ruefully that Ford history is full of difficult, even chaotic, executive changes.

"In many ways, Alan's best act is his final act by giving the company this wonderful opportunity to have an amazing transition," Bill Ford said.